Amniotic Mesenchymal Stromal Cells Exhibit Preferential Osteogenic and Chondrogenic Differentiation and Enhanced Matrix Production Compared With Adipose Mesenchymal Stromal Cells.

BACKGROUND: Therapeutic efficacy of various mesenchymal stromal cell (MSC) types for orthopaedic applications is currently being investigated. While the concept of MSC therapy is well grounded in the basic science of healing and regeneration, little is known about individual MSC populations in terms of their propensity to promote the repair and/or regeneration of specific musculoskeletal tissues. Two promising MSC sources, adipose and amnion, have each demonstrated differentiation and extracellular matrix (ECM) production in the setting of musculoskeletal tissue regeneration. However, no study to date has directly compared the differentiation potential of these 2 MSC populations.

PURPOSE: To compare the ability of human adipose- and amnion-derived MSCs to undergo osteogenic and chondrogenic differentiation.

STUDY DESIGN: Controlled laboratory study.

METHODS: MSC populations from the human term amnion were quantified and characterized via cell counting, histologic assessment, and flow cytometry. Differentiation of these cells in comparison to commercially purchased human adipose-derived mesenchymal stromal cells (hADSCs) in the presence and absence of differentiation media was evaluated via reverse transcription polymerase chain reaction (PCR) for bone and cartilage gene transcript markers and histology/immunohistochemistry to examine ECM production. Analysis of variance and paired t tests were performed to compare results across all cell groups investigated.

RESULTS: The authors confirmed that the human term amnion contains 2 primary cell types demonstrating MSC characteristics-(1) human amniotic epithelial cells (hAECs) and (2) human amniotic mesenchymal stromal cells (hAMSCs)-and each exhibited more than 90% staining for MSC surface markers (CD90, CD105, CD73). Average viable hAEC and hAMSC yields at harvest were 2.3 × 106 ± 3.7 × 105 and 1.6 × 106 ± 4.7 × 105 per milliliter of amnion, respectively. As well, hAECs and hAMSCs demonstrated significantly greater osteocalcin ( P = .025), aggrecan ( P < .0001), and collagen type 2 ( P = .044) gene expression compared with hADSCs, respectively, after culture in differentiation medium. Moreover, both hAECs and hAMSCs produced significantly greater quantities of mineralized ( P < .0001) and cartilaginous ( P = .0004) matrix at earlier time points compared with hADSCs when cultured under identical osteogenic and chondrogenic differentiation conditions, respectively.

CONCLUSION: Amnion-derived MSCs demonstrate a greater differentiation potential toward bone and cartilage compared with hADSCs.

CLINICAL RELEVANCE: Amniotic MSCs may be the source of choice in the regenerative treatment of bone or osteochondral musculoskeletal disease. They show significantly higher yields and better differentiation toward these tissues than MSCs derived from adipose.